The present invention relates to assays involving specific binding, especially immunoassays.
In particular, the invention relates to analytical devices which are suitable for use in the home, clinic or doctor""s surgery and which are intended to give an analytical result rapidly and which require the minimum degree of skill and involvement from the user. The use of test devices in the home to test for pregnancy and fertile period (ovulation) is now commonplace.
In the specification of UK patent application GB 2204398A we describe test devices which are readily usable even by an unskilled person and which typically merely require that some portion of the device is contacted with a sample (e.g. urine in the case of a pregnancy or ovulation test) and thereafter no further actions are required by the user before an analytical result can be observed. The analytical result can be observable within a matter of minutes following sample application, e.g. ten minutes or less.
The use of reagent-impregnated test strips in specific binding assays, such as immunoassays, has previously been proposed. In such procedures a sample is applied to one portion of the test strip and is allowed to permeate through the strip material, usually with the aid of an eluting solvent such as water. In so doing, the sample progresses into or through a detection zone in the test strip wherein a specific binding reagent is immobilised. Analyte present in the sample can participate in a sandwich or a competition reaction within the detection zone, with a labelled reagent which can also be incorporated in the test strip or applied thereto. Examples of prior proposals utilising these principles are given in Thyroid Diagnostics Inc GB 1589234, Boots-Celltech Diagnostics Limited EP 0225054, Syntex (USA) Inc EP 0183442, and Behringwerke AG EP 0186799.
The present invention provides an analytical test device incorporating a dry porous carrier to which a liquid sample suspected of containing an analyte can be applied indirectly, the device also incorporating a labelled specific binding reagent which is freely mobile in the porous carrier when in the moist state, and an unlabelled specific binding reagent which is permanently immobilised in a detection zone on the carrier material, the labelled and unlabelled specific binding reagents being capable of participating in either a sandwich reaction or a competition reaction in the presence of the analyte, in which prior to the application to the device of a liquid sample suspected of containing the analyte, the labelled specific binding reagent is retained in the dry state in a macroporous body through which the applied liquid sample must pass en route to the porous carrier material, the labelled specific binding reagent being freely soluble or dispersible in any liquid sample which enters the macroporous body.
The invention also encompasses a macroporous body containing in the dry state a labelled specific binding reagent that is freely soluble or dispersible in an aqueous sample that may be applied to the macroporous body. The invention further encompasses any analytical device that incorporates such a macroporous body together with a test strip or the like into which liquid sample carrying dissolved or dispersed labelled specific binding reagent can flow from the macroporous body. The invention also encompasses the use of such a macroporous body to facilitate the uptake of a labelled specific binding agent by a liquid sample before such a sample is analysed on a test strip or the like.